Spoof Surface Plasmon Polaritons Structure Research Articles

Multifunctional design of hierarchical corrugated metamaterial absorber realized by carbon fiber stitching

Carbon fiber (CF) which has both mechanical and electromagnetic (EM) characteristics can achieve multiple functions by special designing, such as load bearing and EM wave absorption. In this work, based on the excellent mechanical properties of hierarchical corrugated sandwich structure (HCSS), a novel CF interlaminar reinforced hierarchical corrugated metamaterial absorber (HCMMA) is constructed. By stitching CF arrays onto the core member face of HCSS, the spoof surface plasmon polaritons (SSPPs) structure is constructed, endowing HCSS with EM wave absorption ability and enhancing its interlaminar mechanical properties. Simulation and experimental results show that the proposed structure achieves efficient absorption (average over 90 %) of 4 - 12 GHz EM wave with an incident angle of 0 - 60°, which realized by the dielectric loss of EM wave and local strong E-filed formed by SSPPs structure. In addition, the stitching of CF arrays effectively limit the local buckling-debonding deformation region of the core member face, which greatly improves its mechanical performances. Thereby the compressive strength and specific compressive strength of the proposed structure is increased by 32.7 % and 16.7 %, respectively. Based on the multifunctional design characteristics of CF, the proposed structure effectively expands the application of composite sandwich structures in the field of multifunctional design.

A compact and narrow-band bandpass filter based on substrate integrated waveguide and spoof surface plasmon polaritons for millimeter-wave applications

This paper presents bandpass filter (BPF) comprising substrate integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs), achieving miniaturized size, low insertion loss in the millimeter-wave band. SIW with single-slotted SSPP structure is employing to obtain the transmission zero (TZ) at the low-frequency part, and by introducing the SIW with rhombic periodic walls to enhance the low-frequency rejection. The target passband and TZ of the high-frequency part are realized by increasing the number of etching slots. Furthermore, we innovatively incorporate nonradiative (NR) slots etched below the SSPP structure to gain high out-of-band rejection level. SIW with rhombic periodic walls and slotted SSPP structure as one unit cell is analyzed and demonstrated. Ultimately, the two SIW unit cells are cascaded together to get better out-of-band rejection characteristics and serve as our final design. To validate the proposed design, the BPF prototype is fabricated and measured, showing good electrical performance in terms of high selectivity, low loss, and compact size.

Design and optimization of spoof surface plasmon polaritons based multi-octave power amplifier using PSO algorithm

In this article, we explore how spoof surface plasmon polaritons (SSPP) theory can be applied to the design of active radio frequency (RF) power amplifiers (PAs). This work utilizes SSPP structures for the design of both input and output matching networks for a multi-octave PA. In order to perform proper impedance matching, the properties of SSPP unit structures are presented and analyzed. A description of the performance of the initial PA has been provided and discussed. Additionally, particle swarm optimization (PSO) is used to further enhance the performance of the PA circuit. In comparison with an embedded gradient method in a commercial tool, the PSO method results in a better optimization result. The fabricated PA is tested and the results indicate that in the frequency range of 0.5 GHz to 2.9 GHz, it achieves an output power of 40.4 dBm to 41.2 dBm, a power added efficiency of 60.5–65%, and an output gain exceeding 10 dB. Compared to recent work, the multi-octave PA in this work broadens bandwidth while maintaining high output power and PAE. To further verify the linearity of the SSPP-based PA, digital pre-distortion (DPD) is implemented. As a result of the DPD, the linearity of the SSPP PA was greatly enhanced.

Demonstration of a terahertz coplanar-strip spoof-surface-plasmon-polariton low-pass filter

There is a growing interest in spoof surface plasmon polariton (SSPP) structures at terahertz (THz) frequencies for applications such as filtering, sensing, and communications. However, to date, there are limited experiments that confirm SSPP characteristics at THz frequencies. The majority of literature focuses on simulation or verification by device scaling to Gigahertz (GHz) frequencies where standard vector network analyzers are readily available. This paper presents the first experimental verification of SSPP characteristics at THz frequencies in a guided wave system using coplanar strip (CPS) feedlines. Specifically, we design three SSPP structures with varying band-edge frequencies (1.04 THz, 0.63 THz, and 0.53 THz), then fabricate and verify the low-pass transmission characteristics using a modified THz-time-domain spectrometer (THz-TDS) system. We find strong agreement between simulation, theory, and experiment.

Balanced Filtering Power Divider based on Odd-mode Hybrid Microstrip and Slotline Spoof Surface Plasmon Polaritons

In this paper, an ultra-wideband balanced filtering power divider (B-FPD) with high common mode (CM) suppression level is proposed. The B-FPD is designed based on the odd mode spoof surface plasmon polaritons (SSPPs), which are constructed by the hybrid folded microstrip and slotline (HFMS) structure. Firstly, the dispersion characteristic and electric field distribution of the HFMS SSPP unit cell are investigated, which can decrease the upper cut-off frequency for size reduction of nearly 50%. Next, an equal balanced power divider with low cut-off frequency is proposed based on the microstrip-to-slotline transition structure and slotline Y-junction. Then, the balanced power divider is used to excite the odd mode of HFMS SSPP structure. An equal B-FPD with center frequency of 4.0 GHz is implemented, and the 3-dB bandwidth covers 0.9 to 7.0 GHz. Finally, the B-FPD with advantages of high CM suppression level and compact size is fabricated and measured.

Single-Conductor Spoof Surface Plasmon Polaritons Transmission Line With Bandpass Feature Based on Embedded Cross-Shaped Resonators

In this brief, cross-shaped resonators (CSRs) are integrated in spoof surface plasmon polaritons (SSPPs) unit, and a novel compact single-conductor SSPPs transmission line (TL) with bandpass feature is proposed. In this design, a unit structure based on classical SSPPs structure embedded with a CSR is proposed. To analyze the proposed unit structure, scattering parameters and ABCD-matrix theories are used. After the theoretical analysis, a SSPPs TL with bandpass filtering property is designed. The simulated passband is from 7.9 to 12.2 GHz with a relative bandwidth of 42%. A prototype is fabricated and measured. The measured results are in agreement well with the simulated ones. This proposed structure is attractive and useful for the design of high integrated SSPPs circuits.

Leaky wave antenna with backfire to endfire beam-scanning capability based on even mode spoof surface plasmon polaritons

In this paper, a leaky wave antenna (LWA) based on even mode excited spoof surface plasmon polaritons (SSPPs) is proposed. The LWA can radiate beams from backfire to endfire as the frequency increases. The proposed LWA is asymmetrically modulated by the method of sinusoidal modulation of the reactance surface at two sides of the SSPP structure, which brings a phase difference between two sides of the antenna. The phase difference produces the field component that radiates the beam in the backfire or endfire direction. In this way, the full-angle beam scanning is realized. Moreover, to reduce the open-stop band effect, an improved LWA with multiperiod modulation and asymmetric units is proposed. The simulated results indicate that the radiation beam steers from backfire to endfire. A prototype of the proposed LWAs is fabricated and measured. The measured results agree well with the simulated ones.

Broadside radiation antenna based on tightly coupled spoof surface plasmon polaritons

A spoof surface plasmon polariton (SSPP) is a hybrid mode of a surface wave in the air and electron oscillation within artificial electromagnetic (EM) media, with the dispersion curve lying below the light line, giving rise to many unique EM properties. In this paper, we investigate the EM properties of tightly coupled SSPP (TC-SSPP) modes and propose a slender broadside antenna based on the TC-SSPP. With the comb structure (CS), dispersion properties of different SSPP modes are firstly analyzed under plane wave illumination, and then we introduce a modified SSPP structure, the broadside-coupled (BC)-CS, to excite and guide TC-SSPP modes. Since TC-SSPP modes can be confined tightly around the slender BC-CS, EM waves can be manipulated within a much more compact space, which is favorable for miniaturization, compactness and the light weight of microwave devices. To demonstrate this, we propose a slender broadside radiation antenna based on the TC-SSPP, using a probe as the feed and a finite-length BC-CS as the radiator. Due to near-field magnetic coupling, the SSPP wave can be excited on the BC-CS. By varying the geometric parameters, the antenna can radiate in the broadside direction. A prototype was designed, fabricated and measured. Both the simulated and measured results verify our design.

Wideband High-Gain Filtering Vivaldi Antenna Design Based on MS and Herringbone SSPP Structure

This paper presents a wideband high gain filtering Vivaldi antenna design that utilizes metasurface (MS) and spoof surface plasmon polariton (SSPP) metamaterial for gain enhancement and filtering performance, respectively. The design includes a set of slits etched on the external edges of the antenna to reduce diffraction current, the SSPP structure with inherent dispersion characteristic etched in the slot-line to inhibit RFI, and a novel ‘Φ’-shaped MS unit cell for wideband gain enhancement. These functional metamaterials jointly contribute to optimized performances, and the proposed prototype shows immunity to RFI above 27 GHz and high gain performance over the wide frequency range from 15 GHz to 27 GHz. For demonstration, the protype is fabricated and measured. Measured results agree well with simulated ones.

Wide-Angle Beam-Scanning Leaky-Wave Antenna Array Based on Hole Array SSPPs

In this letter, a leaky-wave antenna (LWA) array based on hole array spoof surface plasmon polaritons (SSPPs) is proposed, which can realize wide frequency beam scanning angle. By etching periodic hole arrays on the upper metal of the defective ground structure, the SSPP structure is formed and the frequency scanning beam is generated by using its higher-order radiation mode characteristics. The radiation mechanisms of the design are explained by using the dispersion relationship, electric field distributions, and space harmonics. The LWA array is fed by a 1 to 4 power divider and achieves good impedance matching within 6-16 GHz bandwidth. The average peak gain value of the proposed LWA antenna array is about 16.86 dBi and the frequency beam scanning range is 91°. The antenna array has the characteristics of easy fabrication, low cost, and high gain performance, which provides a new design concept for wide-scanning-angle LWA Array and can meet the demand of high gain requirements in radar and other related fields.

A Linearly and Circularly Polarization-Reconfigurable Leaky Wave Antenna Based on SSPPs-HSIW

In this manuscript, a reconfigurable leaky wave antenna is proposed with linearly polarized and circularly polarized properties, which is composed of two layers with feeding waveguide and radiation elements. The bottom layer is a half-mode substrate integrated waveguide etched with a spoof surface plasmon polaritons structure as a high-dispersion feeding waveguide to excite 8 circular patches as radiation elements in the top layer. In a unit element, the horizontal linear polarization (HLP) and right-hand circular polarization (RHCP) radiation are switched using a p-i-n diode crossing a slot of a circular metal patch. HLP performance is achieved as the p-i-n diode is switched off, and RHCP is achieved as the p-i-n diode is switched on. The measured results verify the design theory and the simulated results. Over the working band of 10.4~12.8 GHz, the proposed antenna can radiate scanning beams covering about a 73° region, including the broadside direction with HLP and RHCP.

A Slow Wave Folded Ridge HMSIW Using Spoof Surface Plasmon Polaritons Structure and Its Application in Coupler Design

In this article, a folded ridge half-mode substrate integrated waveguide (FRHMSIW) combined with the novel spoof surface plasmon polaritons (SSPP) is proposed to reduce both the lateral size and the longitudinal size. The SSPP structure consisting of sub-wavelength U-shaped grooves, metal patches and metal blind holes is loaded into the FRHMSIW. Firstly, the SSPP increases the effective permeability and permittivity in the waveguide, which can decrease the cutoff frequency and hence reduce the lateral size. Secondly, the SSPP has slow-wave effect, which can reduce the longitudinal size of the waveguide. Analytical formulas of the effective permeability and permittivity are derived based on anisotropic media theory, which are verified by comparing the calculation results with full wave simulation results. According to the derived analytical formulas, a prototype of the proposed FRHMSIW-SSPP waveguide is designed and fabricated using the PCB process. The measurement results show that the proposed waveguide reduces lateral width by 78.7% and the longitudinal dimension by more than 74% compared with the classical SIW with the same cutoff frequency. Subsequently, the FRHMSIW-SSPP structure is applied to design a 3-dB coupler. Results show that the coupler based on the FRHMSIW-SSPP can reduce the surface area by 92.5% compared with the classical SIW coupler.

Mode Composite Substrate Integrated Coaxial Line Based on Substrate Integrated Coaxial Line and Periodic L-Shaped SSPP Structure

In this paper, a mode composite substrate integrated coaxial line (MCSICL) is proposed for transmitting fundamental mode and first high-order mode in dual frequency bands. The MCSICL consists of substrate integrated coaxial line (SICL) and periodic L-shaped spoof surface plasmon polariton (SSPP) structure etched on the inner conductor of the SICL. By introducing the L-shaped SSPP structure, the bandwidth of the fundamental mode of the SICL can be suppressed without changing the cut-off frequency of the first high-order mode. Therefore, the proposed MCSICL can transmit signals at the low-frequency band with the fundamental mode and at the high-frequency band with the first high-order mode. The equivalent circuit model is built to analyze the propagation properties of the MCSICL. In addition, to excite the two modes independently, a grounded coplanar waveguide (GCPW) to MCSICL transition and a microstrip line (ML) to MCSICL transition are designed. The MCSICL with the transitions is fabricated under the printed circuit boards (PCB) process. Measurement results show that the MCSICL can propagate the fundamental mode from dc to 30 GHz and the first high-order mode from 42 to 60 GHz, and the isolation between the two modes is larger than 30 dB.

Reconfigurable broad-band rejection filter based on spoof surface plasmon polaritons

In this paper, we describe a new approach for constructing a broad-band tunable rejection filter based on reconfigurable spoof surface plasmon polaritons (SSPP) whose center frequency can be tuned by altering the capacitance of a varactor diode. The filter structure is composed of SSPP waveguide with double split-rings. We have analyzed and discussed the dispersion characteristics of the filter unit structure and S-parameters of the filter. The filter’s rejection band can be tuned in real-time within the frequency range of 6.4 GHz–10.2 GHz, the rejection strength can reach a positive effect, and the transmission loss in the passband can also be less than 2 dB. When a varactor diode was loaded with the same capacitance, the filter produced one rejection band, and when the varactor diode was loaded with two sets of capacitances, the filter produced two rejection bands. From the results, the filter expands microwave communication possibilities. Furthermore, SSPP structures deliver better field confinement and more substantial field augmentation than standard approaches (microstrip filters), which is beneficial for many communication system applications.

An On-Chip Bandpass Filter Using Complementary Slit-Ring-Resonator-Loaded Spoof Surface Plasmon Polaritons with a Flexible Notch-Band

In this paper, an on-chip bandpass filter with enhanced notch-band is proposed based on the artificial spoof surface plasmon polariton (SSPP) structure around 60 GHz. The shapes of the tabs are modified to incorporate complementary slit-ring resonators (CSRRs) between tabs. The passband is produced by the first higher mode of the SSPP structure. By adding CSRRs, two notch frequencies have been produced in the passband. The advantage of the proposed structure is that these two transmission zeros are almost independent of each other and they do not have much impact on the frequency of the passband. Based on the measured results, the proposed filter has an insertion loss of 2.6 dB with the bandwidth of 14.3 GHz. The return loss is better than 12 dB. The notch-band has a bandwidth of 3.3 GHz with a suppression level over 20 dB. The proposed filter can be applied in the shared millimeter waveband of 5G communication systems.

PSO-Algorithm-Assisted Design of Compact SSPP Transmission Line

This letter proposes a compact spoof surface plasmon polariton (SSPP) transmission line (TL) structure. The particle swarm optimization (PSO) algorithm is utilized to numerically optimize the traditional rectangular groove SSPP structure. The SSPP unit cell is pixelated into 23 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 9 pixels with a resolution of 0.2 mm, and the asymptotic frequency is reduced to 5.4 GHz through optimization. The developed SSPP TL exhibits a compact structure, and its electrical dimension is only about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.842\lambda _{g} \times 0.28\lambda _{g}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{g}$ </tex-math></inline-formula> is the wavelength of the cutoff frequency. A prototype of the developed SSPP TL is fabricated and tested, and the experimental result agrees well with the simulated one. The proposed optimization approach is applicable to both single- and dual-conductor SSPP structures. The results are of great significance to the miniaturization of components and circuits based on SSPP.

Design of High-Gain Single-Layer Endfire Antenna Using Phase-Reversed Asymmetric Spoof Surface Plasmon Polaritons

We present a novel endfire antenna based on asymmetric spoof surface plasmon polaritons (SSPPs) and phase-reversal technique. SSPPs structure allows it to be fabricated on a single-layer printed circuit board. Asymmetric SSPPs elements were employed to fulfill the condition of endfire radiation, and meanwhile, phase-reversal technique provides a high gain for the antenna. To verify the proposed design principle, a prototype was fabricated and measured. It exhibits a peak gain of 16.2 dBi within the operational frequency band of 17–19 GHz, featuring the highest endfire gain among all single-layer designs.

Analysis, Reduction, and Utilization of Loss in Reconfigurable Spoof Surface Plasmon Polaritons

Reconfigurability of dispersion properties of spoof surface plasmon polaritons (SSPPs) have been realized by loading tunable elements such as varactors and p-i-n diodes. However, the parasitic resistance of tunable elements will lead to transmission loss of SSPPs, which still lacks investigation. In this article, we propose to comprehensively answer three critical questions in this area: 1) how to analyze the loss of reconfigurable SSPPs; 2) how to reduce the loss of reconfigurable SSPPs; and 3) how to utilize the loss of reconfigurable SSPPs. For the first question, the complex characteristic impedance of reconfigurable SSPPs is theoretically obtained, which indicates the mechanism of the enhanced loss in reconfigurable SSPPs. For the second question, a low-loss reconfigurable SSPP structure loading parallel varactors is proposed to reduce and reconfigure the loss of reconfigurable SSPPs. For the third question, a multifunctional 2-unit antenna array is designed and tested using a feeding network composed of the loss-reconfigurable SSPPs. Experimental results demonstrate that two functions of sum-difference beam forming and amplitude modulation are achieved by the single sample. Thus the technique of loss reconfiguration in SSPPs may find wide applications in efficiency-sensitive circuits and smart microwave systems in the future.

Wideband high gain differential Vivaldi antenna design based on exponential spoof surface plasmon polaritons metamaterial

In this paper, a wideband high gain Vivaldi antenna based on spoof surface plasmon polaritons metamaterial for radio astronomy application is proposed. The height of the spoof surface plasmon polaritons structures fits the exponential function, thus the structure is named exponential spoof surface plasmon polaritons (ESSPP) metamaterial. With the exponential heights, the ESSPP metamaterial could correct the phase difference in a wide band, the gain is improved in the wide frequency range from 3 GHz to 9 GHz, and the proposed antenna exhibits stable radiation patterns with an average gain of 10.6 dBi.

Ultra-Wideband Planar End-Fire Antenna Based on High-Order Modes of Spoof Surface Plasmon Polaritons

In this article, an ultrawideband planar end-fire antenna based on high-order modes of spoof surface plasmon polaritons (SSPPs) is proposed. First, a quad-band end-fire antenna is designed by using the first four high-order SSPP modes. An SSPP transmission line with gradually decreasing groove depth is used to radiate the high-order modes. Moreover, to improve the gain and sidelobe level at high frequencies, the SSPP units in the quad-band antenna are tilted. Then, an SSPP structure consisting of a periodic array of metal strips is proposed. By adding two arrays of tilted I-shaped strip resonators to the quad-band antenna, the first two bandgaps are eliminated. The proposed antenna achieves a fractional bandwidth of 140.8% from 6.9 to 39.7 GHz. Minimum and maximum measured gains of 6.4 and 15.2 dBi are achieved at 6.9 and 38 GHz, respectively. The proposed antenna has a great potential for applications in imaging and wireless communication.